1. Field of the Invention
The present invention relates to a fundus camera for photographing a fundus of an eye to be examined.
2. Description of Related Art
A fundus camera of a non-mydriasis type is well-known to photograph an image of a fundus when an eye to be examined is under a non-mydiasis condition without using mydriatics. Conventionally, as to a fundus camera of the non-mydriasis type, a pop-up mirror having regular mirror coating is used to switch between an optical path of an observation optical system (this optical path may also be referred to simply as an observation optical path, hereinafter) in which the fundus is observed by using infrared light and an optical path of a photographing optical system (this optical path may also be referred to simply as a photographing optical path, hereinafter) in which the fundus is photographed by visible light emitted from a flash lamp or the like.
Also, as to a fundus camera of the non-mydriasis type, it is preferable that a fixation light for guiding a sight line of an examinee be disposed in an optical system thereof. When a fundus camera has a pop-up mirror, it is possible that the fixation light is disposed on the observation optical path switched by the pop-up mirror.
However, in addition to that a mechanism having a pop-up mirror requires a control sequence in which the pop-up mirror synchronizes with a flash lamp and the like and that it complicates a driving mechanism, it has a disadvantage of driving sounds and vibrations at the time of photographing.
Recently, a fundus camera having a dichroic mirror instead of a pop-up mirror to guide visible light to a photographing optical path and infrared light to an observation optical path has been proposed. However, a fixation light emitting visible light is never disposed on the observation optical path divided by using a dichroic mirror. In this structure, though it may be possible that an extra beam splitter is disposed on the photographing optical path, and that a fixation light is disposed on an optical path divided by the beam splitter, it is disadvantageous because light quantity for photographing may decrease. Furthermore, although it is possible that a fixation light is disposed in the same position as a focus index for adjusting the focus, it may be difficult to arrange a mechanism for movement when the fixation light needs to be moved to guide a sight line.
The present invention has been made in view of the above circumstances and has an object to overcome the above problems and to provide a fundus camera having a simplified unit mechanism, wherein an internal fixation light is disposed at a suitable position for efficiently guiding a sight line.
Additional objects and advantages of the invention will be set forth in part in the description which follows and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the objects and in accordance with the purpose of the present invention, as embodied and broadly described herein, a fundus camera for photographing a fundus of an eye to be examined, the camera comprising an illumination optical system for illuminating the fundus of the eye with visible illumination light for photographing and with invisible illumination light for observation, a photographing optical system having a first photographic element, for photographing an image of the fundus with visible reflection light from the fundus, an observation optical system having a first optical path shared with the photographing optical system, a second optical path divided from an optical path of the photographing optical system by a first wavelength-selecting mirror, a third optical path further divided from the second optical path by a light-dividing member, and a second photographic element disposed on the third optical path, for photographing an image of the fundus with invisible reflection light from the fundus, wherein the first wavelength-selecting mirror has a wavelength-selecting property of transmitting either approximately all of an invisible wavelength range and a part of a visible wavelength range or almost all of the visible wavelength range and reflecting the other, and a fixation target projection optical system having the first optical path, the second optical path, a fourth optical path divided from the third optical path by the light-dividing member, and a light source for eye fixation emitting visible light disposed at a conjugate position with a photographing surface of the second photographic element on the fourth optical path.